The Demographic and Health Surveys (DHS), including 260 nationally-representative household surveys from 90 developing countries, are the principal source of information on pressing health and demographic issues in the developing world. Despite the explicitly comparative nature of DHS, researchers have overwhelmingly used these data to conduct single-survey analyses. There are several reasons for this: the documentation is unwieldy when using multiple DHS surveys; survey questions vary over time and across countries; and sub- national regional comparability is often difficult to assess. Furthermore, current tools inadvertently lure researchers into some unwarranted assumptions about comparability while leading them away from other valid comparisons. The Integrated Demographic and Health Series (IDHS) will develop integrated data, dissemination software, and associated metadata that will make comparative analyses of DHS data dramatically easier. The data will be disseminated without cost through an innovative user interface that will improve search, discovery, research design, and data access. IDHS will reduce wasteful duplication of researcher effort, eliminate common errors, make findings easier to replicate, and facilitate sophisticated and powerful new comparative analyses in many research domains. The work can be divided into six specific tasks: (1) Develop user-friendly web-based data access tools so researchers can exploit the comparative potential of DHS data. (2) Provide access to documentation on a cross-survey and variable-specific basis. (3) Create search and discovery tools to allow researchers to locate variables across surveys. (4) Harmonize variable codes across time and space, without loss of information, and (whenever possible) harmonize sub-national geographic codes. (5) Produce tools allowing users to easily construct customized variables that capitalize on rich information embedded in the complex structure of DHS data, such as the number of surviving female children or the age of the respondent's spouse. (6) Compile consistently structured metadata for all DHS data. IDHS will unlock access to one of the richest data sources for the developing world, and will open up new terrain for comparative investigation of health, demography, and economics in a global context.